Keratoconus is a progressive eye condition where the cornea, the clear, dome-shaped front surface of the eye, gradually thins and bulges outward into a cone shape. This change causes light entering the eye to become unfocused, leading to distorted vision. This article explains the visual experiences of those living with keratoconus.
How Keratoconus Affects Vision
The cornea, typically a smooth, rounded surface, plays a significant role in focusing light onto the retina at the back of the eye. With keratoconus, the cornea loses its regular dome shape and develops an irregular, conical protrusion. This altered curvature prevents light rays from converging precisely on the retina, causing light to scatter across multiple points instead of a single, sharp focal point.
This scattering results in irregular astigmatism, a refractive error that standard eyeglasses often cannot fully correct. The steepening of the cornea also causes the eye to become more nearsighted. Consequently, the visual information transmitted to the brain is unclear, leading to a range of visual disturbances.
The Specific Visual Distortions
People with keratoconus commonly report a variety of distinct visual distortions. One frequent symptom is ghosting, also known as monocular diplopia, where images appear duplicated or smeared, often observed in only one eye. This happens because the irregular corneal surface creates multiple, slightly offset images of a single object on the retina. For example, a single street light might appear as several overlapping lights.
Blurred and distorted vision is another pervasive complaint, making objects appear fuzzy or wavy rather than clear and defined. Straight lines, such as those on window blinds or doorframes, might look bent or distorted. This general lack of clarity is not easily remedied with conventional corrective lenses due to the corneal irregularity.
Glare, halos, and starbursts are particularly troublesome symptoms, especially in low-light conditions or at night. Glare manifests as excessive brightness that obscures details, while halos appear as rings around light sources. Starbursts are characterized by light rays extending outwards from bright points, creating a star-like pattern. These phenomena occur because the distorted cornea scatters incoming light, creating distracting visual artifacts.
Light sensitivity, or photophobia, is also a common experience, where bright lights can cause discomfort or even pain. Sunlight or glare from artificial sources may necessitate squinting or avoidance of well-lit environments. Reduced night vision is a significant challenge, as glare, halos, and distorted vision are often exacerbated in low-light conditions. This makes tasks like driving at night particularly difficult and potentially dangerous.
Vision Changes Over Time
Keratoconus is a progressive condition, meaning its visual symptoms typically worsen over time as the corneal thinning and bulging advance. The disease often begins during the teenage years or early adulthood, with symptoms that might initially be mild and easily mistaken for common refractive errors. Early signs can include a slight blurring or distortion of vision, along with increased light sensitivity.
As the condition progresses, usually over a period of 10 to 20 years, the visual impact becomes more pronounced and disruptive. This progression leads to more severe blurring, increased nearsightedness, and worsening astigmatism. The rate of progression varies considerably among individuals; some may experience rapid changes, while others have a slower, more gradual worsening over many years. The younger a person is at diagnosis, the higher the likelihood of more rapid progression.
Navigating Daily Life with Keratoconus
The specific visual distortions caused by keratoconus can profoundly affect a person’s ability to perform everyday tasks, impacting their quality of life. Driving, especially at night, often becomes a significant challenge due to increased glare, halos, and starbursts from headlights and streetlights. The difficulty judging distances and perceiving clear images in low light can make night driving hazardous.
Reading can also become strenuous as words may appear blurred, distorted, or ghosted, with letters overlapping. This requires increased effort and can lead to eye strain and fatigue during prolonged close-up work. Similarly, using computers and other digital devices presents difficulties, as bright lights can exacerbate glare and light sensitivity, making text and images hard to discern.
Recognizing faces can also be challenging, as irregular vision might blur or distort facial features, affecting social interactions. Frequent changes in eyeglass prescriptions are common as the condition progresses. Adapting to these persistent visual challenges requires ongoing adjustments.